The goal of this project is to use an infection-independent cell-based assay to identify compounds that inhibit respiratory syncytial virus (RSV). The basis of this bioassay is expression of a reporter gene from an artificial viral genome present within the cytoplasm of transfected cells. Significant advances have been made in identifying the cis-acting elements and trans-acting factors involved in replication of many pathogenic negative-strand RNA viruses including RSV. Negative-strand RNA viruses include some of the most notorious human pathogens and cause significant worldwide morbidity and mortality due to severe respiratory disease and hemorrhagic fever syndromes. Unfortunately very few therapeutic agents are available to treat infection with these viruses. Efforts to find new antiviral agents will require methods that are amenable to HTS. In this application the investigators describe their plans to use novel cell-based assays to identify compounds with anti-RSV activity. To identify 'hits' that inhibit replication of RSV the applicants plan to screen a unique library of natural compounds and several novel libraries of synthetic compounds. Apath's partner has developed a proprietary system for making compound libraries from plant-based material. High abundance compounds that lack drug like properties are removed, and the remaining compounds are chromatographically fractionated into distinct peaks, which are provided to Apath, LLC as arrays in bar-coded 96-well plates. Synthetic chemical libraries have been obtained from commercial sources that use novel approaches to make diverse compounds from well-conceived scaffolds. Antiviral activity of all 'hits' will be confirmed in secondary assays to measure inhibition of RSV directly. The investigators will identify compounds with the most promising chemical and biological profiles to pursue as potential anti-RSV drugs. The applicants also plan to identify the targets of the inhibitory compounds through biochemical and genetic approaches.